Watering Your Cannabis: How To Fix Over And Underwatering
Overwatering and under watering your cannabis plants can cause multiple symptoms and may even slow down growth. It’s all about understanding your plants and finding a sweet spot. We explore how to recognize and fix these issues, as well as take a look at the importance of water quality in general.
There are many contributing factors involved when it comes to a successful and bountiful cannabis grow. Lighting, nutrients, airflow, and humidity all play important roles in optimal growth and vibrancy of a crop. Water, however, is one of the most important aspects of keeping cannabis plants healthy and strong.
Watering isn’t always as simple as it may seem. Many growers are under the impression that completely saturating their crop with water each day is all it takes to help plants obtain their aquatic requirements.
The truth is, there is much more to the watering process. Watering cannabis plants is a balancing act that takes some time and experimentation to perfect. Too much water can lead to some serious problems for plants and may obstruct oxygen intake. On the other end of the spectrum, too little water can lead to extremely dry conditions that will leave cannabis plants thirsty, eventually causing them to wilt.
We take a look how to recognise if you are over or under watering, and how to fix it.
OVERWATERING YOUR PLANTS
Overwatering is an easy mistake to make when growing cannabis, and is most likely caused by worrying that plants need constant doses of water. It is a pitfall novice often fall into.
Cannabis plants actually use their root systems to breath air, in addition to uptaking water, and if their roots are constantly swamped in water, they will begin to drown.
1. One primary symptom of overwatering is drooping leaves. However, it is not the same kind of droop you see when underwatered – where leaves look wilted. It is the opposite in fact. Leaves are so full of water, that they are being forced to curl in on themselves. It results in them becoming very firm.
2. Additionally, the rate of growth of overwatered plants will slow down dramatically or may even come to almost a complete halt. This is due to the anaerobic conditions that arise due to the lack of oxygen accessible to the root system.
3. Another symptom of overwatering a cannabis plant is yellowing of the leaves. This is a sign of a nutrient problem, that is a side-effect of overwatering.
If you are experiencing any of these symptoms within your plants and believe the root cause is overwatering, the best thing to do is water less often. Wait for the top layer of soil to look and feel dry before watering again. A good test is to put your index finger in the soil up to the knuckle. if it is dry, consider watering.
Also, make sure each plant has adequate drainage and that water isn’t building up too much in the bottom of the pots or containers that they are housed within. You want excess water to drain out of the containers, leaving soil moist but not waterlogged.
UNDERWATERING YOUR PLANTS
1. Underwatered cannabis plants will look very weak, lifeless, and will show signs of wilting. Its no wonder they begin to look this way considering the vital role of water in plant physiology. The wilting of underwatered cannabis is different from the plump curling of overwatering – even if only subtly. Leaves will be fragile, brittle and even papery. They will look lifeless and drab. Another sign of an under watered cannabis plant an extremely dry growing medium, such as crispy soil.
2. Underwatering occurs when growers simply aren’t meeting their plant’s demands. Without adequate water, the root system will dry up and growth and yield may be reduced. Be sure to water your plant when the top inch of soil has dried out. Leaving it any longer than this may start to have detrimental effects.
3. One aspect that may cause underwatering is not using the correct pot size at certain stages of growth. For example, growing a small seedling in a large pot may reduce the plant’s chances of uptaking enough water, as the small root system doesn’t have a chance to uptake water before it drains away.
WATER QUALITY IS PARAMOUNT
As well as watering frequency, the quality of the water used to supply a cannabis crop is also a highly important consideration.
Cannabis plants consist of approximately 90% water, and the substance is required during various vital physiological process such as photosynthesis and transpiration. When using a poor quality water source to supply cannabis plants, these processes may be less efficient than they can be, or in worst case scenarios, disruptive.
When these disruptions occur, symptoms may manifest that appear almost identical to an array of other conditions such as over or under fertilisation, under-watering, and possibly even heat stress. This is a perfect example of why to always double and triple check the root cause of the problem when troubleshooting health issue of cannabis plants.
HOW OFTEN DO YOU NEED TO WATER YOUR PLANTS?
This question actually has many different answers, as many different variables are at play. For this reason, there is no exact answer. For example, temperature, humidity, and other environmental factors can all change how often water will be required.
However, there are telltale signs that will display it’s time to once again water your plants. Checking the top inch of soil is a promising way to identify this. Wait for this section of the soil to be dry before watering again in order to avoid overwatering. Once you have done so multiple times, you should start to figure out how long it takes in between each watering, and then you can go by that length of time instead.
Paying close attention to your plants leaves is another way to tell if its time to water. Of course, waiting long enough to symptoms to arrive is not optimal, but any signs of wilting should immediately be followed by a dose of water.
Before the growing process, check the quality of your water source. One important factor when it comes to water quality is pH. pH is a numeric scale used to measure the acidity or alkalinity of a solution, with the middle value of 7 representing neutral. Numbers less than 7 represent acidity and numbers above 7 display alkalinity.
PH that is either too high or too low can cause problems in cannabis plants, as the pH of the water source can dictate a plant’s ability to absorb nutrients. Too low or too high pH water can affect the pH of your grow medium over time, which results in symptoms that look identical to those caused by certain nutritional problems.
Cannabis plants tend to thrive at a pH of around 6.5. pH can be measured extremely easily by simply applying a pH metre around a water runoff sample. Runoff is water that drains from your grow container, having passed through your grow medium. If the pH is either too high or too low, pH up and down products can be used to return it to normal levels.
PPM is another important factor when it comes to water quality. Ppm, or parts per million, is a method of measuring the amount of minerals that have dissolved into the water source being used. So, a reading of 90ppm will indicate that there are 90 milligrams per litre of minerals present within the water source.
Being aware of the PPM within water allows growers to avoid giving their plants too many or too little minerals. A lack of minerals may lead to deficiencies, whereas too many may cause burning to occur. Cannabis plants prefer a ppm of around 500 when in the vegetative phase, and favour a ppm of around 1000 during the flowering stage of the grow cycle.
TDS meters, devices that measure total dissolved solids, can be used to measure the ppm of a water source.
Monitoring ppm is quite advanced, and while useful, is not essential for novices finding their feet. Just bear it in mind as you look to expand your knowledge and skill.
REVERSE OSMOSIS WATER
Although the total dissolved solids within your water profile might be adequate, not all substances within a water source are beneficial for your cannabis crop. Water might be contaminated with other factors such as pollutants and bacteria. Reverse osmosis filters are a great option to almost completely remove everything within a water source, allowing growers to add back only what they want their plants to come into contact with.
Reverse osmosis filters are capable of removing between 95-99% of dissolved salts within a water sample and is therefore a standard method of cleaning water on an industrial scale.
Once again, using reverse osmosis water is an advanced growing technique.
With the above in mind, you should be well on your way to understanding how over and underwatering affects your plants – as well as overall water quality in general.
TESTING YOUR WATER RUNOFF
To produce healthy plants, you need to keep a close eye on the amount of nutrients your plants are receiving. To do this, use trays to catch the runoff when you water your plants, and analyse both its pH and PPM (parts per million).
WHAT PH SHOULD YOUR RUNOFF BE?
Cannabis plants tend to thrive at a pH of around 6.5. To check your pH, simply test the runoff using a pH meter. Our pH tester by Hanna Instruments is super simple to use and offers fast and accurate readings. If your pH is either too high or too low, you can use pH regulators to bring it up or down.
Too many fertiliser salts can obstruct nutrient uptake and cause wilting. Use the DiST 4 Pocket Conductivity Tester for accurate readings.
Too many fertiliser salts can obstruct nutrient uptake and cause wilting. Use the DiST 4 Pocket Conductivity Tester for accurate readings.
We explore how to recognise and fix cannabis over and underwatering, as well as the importance of good quality water.
Common Solutions for Wilting/ Drooping Leaves
Please help us! We have a few young seedlings, about four weeks old now, and they all have wilting or drooping leaves. The color is good, but the leaves are heavy and sagging. Some have wilted to nearly nothing. We water them twice a day. Please save our babies! Thank you!
— Margie & Anna V. via the mailbag at [email protected]
Thanks for writing us with a very good question. We actually get a ton of “leaf wilting” questions in the mailbag every month, so I am happy to finally answer this one!
It is important to understand that wilting/drooping leaves means that there is a deficiency somewhere within the plant. A deficiency can come from one or multiple areas (let’s hope it is just one). The primary areas a plant receives nutrition from are: light (photon energy), atmosphere (CO2 and O2) and medium (H2O and mineral nutrients).
An example of healthy plants, with leaves cupped upwards toward the light. (Photo by Nico Escondido)
Wilting/ drooping leaves are most commonly a sign of problems with water and/or nutrients. You did not mention any discoloration of the leaves, which is good, leaving us to focus mostly on hydration and not mineral deficiencies. But to start, we need to make a distinction between the terms wilting and drooping.
When it comes to drooping leaves, the issue is most often due to over-watering, believe it or not. Sometimes water stress, such as “drowned roots,” can cause abscisic acid to build up, closing down the leaf stomata and creating problems in both respiration and photosynthesis.
Wilting leaves, which is actually defined as having water loss or being dehydrated, is obviously associated with a lack of water. Wilting leaves will be dry to the touch and even a bit crumbly. Because you water twice daily and state the leaves are “heavy,” my guess here is the former—over-watering.
Over-watering can also cause the soil or grow medium to compress and suffocate the roots, which respire by breathing in oxygen (O2) during the dark or night cycle. The top third of the root structure contains air-specialized roots for this purpose (while the bottom third of the root structure is known as “water roots”). If the grow medium becomes too compacted, the breathable roots may lose their ability to respire and absorb oxygen, which they use to convert sugars to energy. Both the loss of oxygen and the build up of abscisic acid will severely weaken steams and leaves of the plant above the surface.
Now, if your plants are more wilting than drooping, meaning they are dry and crumbling, the issue is more likely to be under-watering. Test the soil for moisture content by pressing your index finger about an inch down into the medium. You should feel some moisture and coolness. While watering plants twice a day sounds like plenty of water, if you are only pouring in a few drops, it might not be enough.
An example of drooping plants, with heavy, wet sagging leaves. (Photo by Nico Escondido)
Generally, good watering practice dictates that you water each plant once, at the start of the day when the sun/ lights come up. Saturate the medium well, until you see the first drops seep out of the bottom of the container. That will be enough water for the day. It is also a good idea to let the medium become fairly dry—at least near the surface of the medium—before attempting to water the plant again. It is important to remember that while the plant itself breathes in CO2, the roots beneath the surface breath in oxygen (O2) during the night cycle. This is an essential part to healthy plant growth and development. And a dry, aerated medium goes a long way in allowing air to permeate the root zone and roots to breathe in their precious O2.
To fix the drooping, allow the medium to dry out overnight (completely) and use a thin stick (i.e., a skewer) to gently poke holes around the surface of the medium to help aerate—taking care not to damage any roots below. Poke around the edges, about an inch or two down, making a circling motion with the stick to make small holes.
Take another thin stick and use it as a support stake, if necessary. Stake it near the base of the plant and rest or tie the main stem to it. Make sure the plant’s main stem and branches are not thin and spindly. If they are, this could also be a sign they are stretching for light. Make sure your plant is directly under the light source and receiving around 18 hours of light per 24 hours to help it vegetate.
You are likely still a few weeks to a month away from being able to switch to a 12/12, light/dark cycle to induce flowering because of this setback with the drooping leaves. However, with some diligence and care, you can easily get your babies to bounce back and have a productive life cycle.
It is important to understand that wilting/drooping leaves means that there is a deficiency somewhere within the plant. A deficiency can come from one or